1. Field of the Invention
This invention relates to a concrete foundation which adapted to be embedded in the ground for supporting a pole thereon. More particularly, this invention relates to a concrete foundation which includes a vertically disposed central section and a base portion which embraces the central section and which engages the same to prevent movement of the central section.
2. Description of the Related Art
All wayside signals on the Union Pacific Railroad previously required a foundation that was buried in the ground to a depth of six feet or so to properly anchor the signal fixtures against the considerable wind-loading brought to bear on their towering surfaces. The foundation itself consisted of concrete sections of manageable size which stacked one on top of the other in several configurations to form a dead weight mass which was held together by four one-inch steel bolts with nuts at each end. While most railroads now have lifting equipment to handle a pre-assembled unit, it was necessary to have a sectionalized foundation when they were manually assembled in the field.
To tie all sections of the foundation together, and also have a six inch or so bolt projection at the top, on which to mount the signal, required four 1×84″ bolts. These bolts, which must be hot-dipped galvanized, together with the required over-sized galvanized nuts and washers, are the most expensive elements of the foundation system.
The Burlington Northern Railroad had a similar “pedestal type” sectional foundation which they used for a number of years. However, once their crews were provided proper lifting equipment, they no longer embraced the notion of using sectional-type foundations and adopted a monolithic unit weighing about two thousand pounds which was buried to a depth of just under five feet. It is designed with deep recesses on all four sides providing excellent earth-compaction and is a very serviceable product.
Because of its monolithic design, it does not require full length bolts as is the case for holding a sectional foundation system together. Since the purpose of the bolts is only to serve as a means to secure the signal fixtures to the foundation shorter lengths of bolts are embedded in the concrete, with the embedded end bent sharply to provide a good anchor in the concrete. Obviously, the set-up concrete prevents the bolts from pulling out or having any movement whatsoever.
While there are other costs associated with the pedestal-type sectional foundations (additional steel wire, galvanizing, more forms, etc.) the main cost is in the hot-dipped galvanized one-inch diameter bolts. Union Pacific foundations require four each 1×84″ (28 feet) versus Burlington Northern foundations which require four each 1×36″ bolts (12 feet).
Before the consolidation trend started 30 years ago, there were perhaps 25 Class I railroads, and each had its own signal foundation standards. Most had some version of the sectional foundation for the reasons described earlier, with the most common utilizing inter-locking concrete sections supplied by the Permacrete Company and were adopted as the AAR (Association of American Railroads) standard.
Railroads using this design included Illinois Central, Kansas City Southern, Missouri Pacific and the eastern railroads which later became Norfolk southern and CSX Systems. The Santa Fe primarily used the galvanized steel foundation supplied by Safetran Corp. The union Pacific has used the pedestal-type sectional for over 50 years. The Burlington Northern and Chicago and Northwestern both adopted the monolithic design before they merged to form respectively the BNSF and the Union Pacific.
Several years ago, there was a fatal accident when a signal crewman died in a cave-in of a hole being dug to install a signal foundation. As a result of this accident, and perhaps others. The railroad involved restricted the depth to which a hole could be dug which might endanger a workman. It is believed the new limit must be around five feet.
For the shorter foundation to provide the required stability, it was necessary to go to a larger base plate than the 32″×32″×4″ called for in their original design. The new base was increased to 57″×57″×6″ and weighed 1620 pounds which added desired stability in addition to the greatly increased horizontal surface for earth compaction.